The invention concerns the field of horology, and more specifically the field of timepieces including date display mechanisms.
Date mechanisms are complex mechanisms.
The date has to be manually corrected for months of less than thirty-one days, in the case of timepieces with a simple calendar mechanism. This correction is generally either performed by rotating the winding stem into a rapid date set position, or by actuating a pusher dedicated to this use.
Updating the date is not always easy, in particular when the user wishes to change the date close to midnight.
Moreover, most known mechanisms do not allow the date to be changed backwards.
U.S. Pat. No. 212,882 in the name of Baillot, presented, in 1879, a date corrector mechanism using a click cooperating, under the action of a pusher, with the toothing of a 31 day wheel to move said wheel forward.
There is known from EP Patent No. 1 115,041 in the name of Chopard Manufacture SA, a rapid manual date corrector mechanism for a movement comprising a winding stem with three axial positions with a sliding pinion and a date star-wheel. This mechanism comprises a rocking corrector lever comprising, at one end thereof, a beak cooperating with the toothing of the date star-wheel, and at the other end thereof, a finger returned by a spring against a cam having at least one lifting piece. This cam is carried by a corrector wheel driven via a kinematic connection by the sliding pinion, when the winding stem is in an intermediate, axial, date correction position. The lifting pieces of the cam are pointed, thus when the winding stem is not in the date setting position, the return spring of the finger on the cam causes said finger to return between two lifting pieces of the cam, so that the beak of the lever is no longer in contact with the date star-wheel. This mechanism allows the date to be advanced by rotating the winding stem in any direction, but it does not allow the date to be moved backwards.
EP Patent No. 1,660,952 in the name of Vaucher Manufacture Fleurier SA discloses a manual date corrector for a simple calendar mechanism and an automatic date corrector for a perpetual calendar. This corrector comprises a means of programming the rectification of the date display according to the number of days of the current month entered by the user or by an automatic mechanism, and a means of retrieving the rectification on the last actual day of the month concerned. This programming means includes a coupling wheel set formed of two coaxial toothed discs which can be driven in opposite directions, one by the thirty-one wheel, and the other by the control means which sets the number of days of the month, so that at the end of the current month, the display means is automatically corrected. These two discs are coupled by a spring and by a click system allowing one disc to rotate independently of the other. The clicks also enable the second disc, which is driven by the control means, firstly to drive the other disc when it is rotating in the first direction, and secondly, not to drive said other disc when it is rotating in the other direction when said second disc then merely winds the spring. In addition to these discs, the programming means includes a finger secured to the thirty-one wheel, a lever which pivots on the second disc and is actuated by the finger on the last day of the current month, and which then actuates another independent lever of the coupling wheel set. This other lever locks the second disc and releases it when actuated, so that, under the action of the spring, the first disc rapidly moves to rectify the date display. This complex device performs correction both manually and automatically, but it too is unable to move the date backwards instead of forwards.
Likewise, EP Patent No. 1 538 494 in the name of Watch-U-License AG is known, which discloses a rapid date setting device comprising a pull-out piece, which is driven by the winding stem and pivots a lever carrying a lever pinion which, in an intermediate position of the winding stem, meshes with a wheel coupled to a date corrector wheel set provided with fingers capable of acting on a date indicator crown. This device requires an intermediate pinion set, and is one-directional.
EP Patent No. 0 230 878 in the name of Complications SA proposes a date corrector comprising a stem driving, via a gear train, a corrector star-wheel which meshes directly with a date star-wheel. This simple system cannot, however, be used permanently since, close to midnight, the date star-wheel is cooperating with an elastic finger of the twenty-four wheel, and any manual intervention is then damaging for the movement. Further, this mechanism can only move the date forwards and not backwards.
A more complex date corrector mechanism for a perpetual calendar is presented by EP Patent No. 1488 290 in the name of Manufacture Roger Dubuis SA. This mechanism is indexed on the position of an annual cam, detected by a sensor, and arranged for automatic operation, but not for manual correction.
However, these known mechanisms all use the kinematic chain of the winding mechanism and the sliding pinion, and the operation of updating the date occurs day by day, is quite fiddly and causes wear of the winding and time-setting mechanism. Above all, although some mechanisms allow the winding stem to rotate in both directions to advance the date, they can only change the date in a single higher date direction, which of course means passing through the change from 31 to 1 in order to return to a lower date than that previously displayed.
EP Patent No. 1 953 611 in the name of Compagnie des Montres Longines, Francillon SA, discloses a two-directional correction mechanism for a display device such as a date mechanism. This mechanism provides a reliable and efficient solution to the problem of correcting the date backwards. Two racks tend to act in opposite ways on the date display wheel. The first rack is controlled by a first lever which cooperates with a snail cam integral with a date wheel, which is in turn driven each day by a finger integral with the twenty-four hour wheel. The second rack is controlled by a second lever, which cooperates with a peripheral cam driven by the winding stem, and this peripheral cam is arranged to move the first lever away from the snail cam. Thus the date wheel can pivot in both directions. However, this improved mechanism includes numerous components, making it relatively expensive, and the space required, particularly as regards the peripheral cam, makes it difficult to adapt to all movements.
EP Application No. 0 871 093 A1 in the name of ORIS is also known, which discloses a manual date indicator corrector mechanism in the form of a toothed ring. A first or second device may be coupled one at a time to the date indicator, as a result of uncoupling means. The first device is used only for correcting the date indicator, and the second device is for correcting the hour and minute hands and the date indicator. The second device is a wheel set comprising a first star-wheel able to mesh with the toothed ring, and a second star-wheel able to mesh with a finger carried by an intermediate wheel. The intermediate wheel meshes with the hour wheel. The uncoupling means is a plate, which carries the wheel set and is returned by the spring, pivoting on an arbour carrying the intermediate wheel. The wheel set is engaged when the first star-wheel meshes with the ring. The wheel set is disengaged when the first device is actuated. The first star-wheel no longer meshes with the ring, whose teeth push those of the first star-wheel out of their trajectory against the return force of the spring. The positions of engagement and disengagement are defined by the position of a pin, secured to the plate, relative to an oblong hole of the plate, which is integral in particular with the spring. This mechanism fits the description of the preamble of the claim of this patent application.